(I tried posting this to the CFWheels Google Group (twice), but for some reason my message never appears. Is that list moderated?)
Here's my problem: I'm working on a social networking app in CF on Wheels, not too dissimilar from the one we're all familiar with in Chris Peters's awesome tutorials. In mine, though, I'm required to display the most recent status message in the user directory. I've got a User model with hasMany("statuses") and a Status model with belongsTo("user"). So here's the code I started with:
users = model("user").findAll(include="userprofile, statuses");
This of course returns one record for every status message in the statuses table. Massive overkill. So next I try:
users = model("user").findAll(include="userprofile, statuses", group="users.id");
Getting closer, but now we're getting the first status record for each user (the lowest status.id), when I want to select for the most recent status. I think in straight SQL I would use a subquery to reorder the statuses first, but that's not available to me in the Wheels ORM. So is there another clean way to achieve this, or will I have to drag a huge query result or object the statuses into my CFML and then filter them out while I loop?
You can grab the most recent status using a calculated property:
// models/User.cfc
function init() {
property(
name="mostRecentStatusMessage",
sql="SELECT message FROM statuses WHERE userid = users.id ORDER BY createdat DESC LIMIT 1,1"
);
}
Of course, the syntax of the SELECT statement will depend on your RDBMS, but that should get you started.
The downside is that you'll need to create a calculated property for each column that you need available in your query.
The other option is to create a method in your model and write custom SQL in <cfquery> tags. That way is perfectly valid as well.
I don't know your exact DB schema, but shouldn't your findAll() look more like something such as this:
statuses = model("status").findAll(include="userprofile(user)", where="userid = users.id");
That should get all statuses from a specific user...or is it that you need it for all users? I'm finding your question a little tricky to work out. What is it you're exactly trying to get returned?
Related
I am trying to write a query that 1) works and 2) shows meaningful information.
However, I can't seem to complete both scenarios. Both bits of code do work to a degree. My SQL query does work by showing all the useful information a user wants but when you click the edit button it doesn't link properly so it won't allow the user to update that row. The other shows only keys and rowid but when you click edit does show the information and allows it to be updated.
So as not to get another down-voted question, I have taken pictures of each scenario to show the problem, but, ultimately, I need to show meaningful information: an id or key isn't meaningful to the vast majority of users.
Here is my code
SELECT APPLICATIONS.APP_ID, APPLICATIONS.SRN, STUDENTS.SURNAME, STUDENTS.FORENAME, APP_STATUS.STATUS, METHODS.METHOD, JOBS.JOB_TITLE, APPLICATIONS.APP_DATE
FROM APPLICATIONS
JOIN STUDENTS
ON APPLICATIONS.SRN = STUDENTS.SRN
JOIN APP_STATUS
ON APPLICATIONS.STATUS_ID = APP_STATUS.STATUS_ID
JOIN METHODS
ON APPLICATIONS.METHOD_ID = METHODS.METHOD_ID
JOIN JOBS
ON APPLICATIONS.JOB_ID = JOBS.JOB_ID;
and here are the pictures of it in action
below is the code that does not show meaningful information but does work.
select "ROWID",
"APP_ID",
"SRN",
"STATUS_ID",
"METHOD_ID",
"JOB_ID",
"APP_DATE"
from "#OWNER#"."APPLICATIONS"
If i knew how to properly use rowid i am sure this is a simple feat but i dont so if i could get any help it would be useful
//edit
who ever renamed this to Application Expression why? what i am using is Apex Application Express it was relevant information that got changed to something wrong which might make it hard for someone with a similar problem to find later.
In the second, simple query, apex can determine which table (and record) you are trying to edit.
In the first query, with the joins, it can't tell which of the five tables in query you want to edit. You probably want to have the edit link pass the primary key of the row from APPLICATIONS to the child page. You would need to build into that page any logic (lists of values etc) that map lookup tables (such as status) to the values needed in the APPLICATIONS table.
I have problem with one query.
Let me explain what I want:
For the sake of bravity let's say that I have three tables:
-Offers
-Ratings
-Users
Now what I want to do is to create SQL query:
I want Offers to be listed with all its fields and additional temporary column that IS NOT storred anywhere called AverageUserScore.
This AverageUserScore is product of grabbing all offers, belonging to particular user and then grabbing all ratings belonging to these offers and then evaluating those ratings average - this average score is AverageUserScore.
To explain it even further, I need this query for Ruby on Rails application. In the browser inside application you can see all offers of other users , with AverageUserScore at the very end, as the last column.
Associations:
Offer has many ratings
Offer belongs to user
Rating belongs to offer
User has many offers
Assumptions made:
You actually have a numeric column (of any type that SQL's AVG is fine with) in your Rating model. I'm using a column ratings.rating in my examples.
AverageUserScore is unconventional, so average_user_score is better.
You don't mind not getting users that have no offers: average rating is not clearly defined for them anyway.
You don't deviate from Rails' conventions far enough to have a primary key other than id.
Displaying offers for each user is a straightforward task: in a loop of #users.each do |user|, you can do user.offers.each do |offer| and be set. The only problem here is that it will execute a separate query for every user. Not good.
The "fetching offers" part is a standard N+1 counter seen even in the guides.
#users = User.includes(:offers).all
The interesting part here is only getting the averages.
For that I'm going to use Arel. It's already part of Rails, ActiveRecord is built on top of it, so you don't need to install anything extra.
You should be able to do a join like this:
User.joins(offers: :ratings)
And this won't get you anything interesting (apart from filtering users that have no offers). Inside though, you'll get a huge set of every rating joined with its corresponding offer and that offer's user. Since we're taking averages per-user we need to group by users.id, effectively making one entry per one users.id value. That is, one per user. A list of users, yes!
Let's stop for a second and make some assignments to make Arel-related code prettier. In fact, we only need two:
users = User.arel_table
ratings = Rating.arel_table
Okay. So. We need to get a list of users (all fields), and for each user fetch an average value seen on his offers' ratings' rating field. So let's compose these SQL expressions:
# users.*
user_fields = users[Arel.star] # Arel.star is a portable SQL "wildcard"
# AVG(ratings.rating) AS average_user_score
average_user_score = ratings[:rating].average.as('average_user_score')
All set. Ready for the final query:
User.includes(:offers) # N+1 counteraction
.joins(offers: :ratings) # dat join
.select(user_fields, average_user_score) # fields we need
.group(users[:id]) # grouping to only get one row per user
I read about createCriteria, and kind of interested on how these works, and its usability in providing values for dropdown box.
So say, i have a table in the database, Resource table, where i have defined the table in the domain class called Resource.groovy. Resource table has a total of 10 columns, where 5 of it are
Material Id
Material description
Resource
Resource Id
Product Code
So using the createCriteria, and i can use just like a query to return the items that i want to
def resList = Resource.createCriteria().list {
and {
eq('resource', resourceInstance)
ne('materialId', '-')
}
}
Where in the above, i want to get the data that matches the resource = resourceInstance, and none of the materialId is equal to '-'.
I want to use the returned data from createCriteria above on my form, where i want to use some of the column on my select dropdown. Below is the code i used for my select dropdown.
<g:select id="resourceId" name="resourceId"
from="${resList}"
disabled="${actionName != 'show' ? false : true}" />
How do i make it so that in a dropdown, it only shows the values taken from column Product Code? I believe the list created using createCriteria returns all 10 columns based on the createCriteria's specification. But i only want to use the Product Column values on my dropdown.
How do i customize the data if in one of the select dropdown in my form, i wanted to show the values as "Resource Id - Resource Description"? The values are combination of more than 1 columns for one select dropdown but i don't know how to combine both in a single select dropdown.
I read that hql and GORM query are better ways of fetching data from table than using createCriteria. Is this true?
Thanks
First of all refer to the document for using select in Grails. To answer all questions:
Yes, the list to select from in the dropdown can be customized. In this case it should be something like from="${resList*.productCode}"
Yes, this can be customized as well with something like
from="${resList.collect { \"${it.resourceId} - ${it.resourceDesc}\" } }"
It depends. If there are associations involved in a domain then using Criteria will lead to eager fetches which might not be required. But with HQL one gets the flexibility of tailoring the query as needed. With latest version of Grails those boundries are minimized a lot. Usage of DetachedCriteria, where queries etc are recommended whereever possible. So it is kind of mixing and matching to the scenario under consideration.
I'm trying to get a "What's new" section working in my Rails app that takes into account new records created for various tables that don't share any relationships. The one thing they do have in common is that they all have a created_at field, which I'm going to use to determine if they're indeed "new" and then I'm wanting to sort the results by that common field. I tried doing this with Sunspot, but I couldn't figure out how to make use of the the result set returned from the Sunspot search...
For instance in my Uploads and Article models I have:
searchable do
time :created_at
end
and in my search action I'll do this:
#updates = Sunspot.search(Upload,Article) do
with(:created_at).greater_than(1.hour.ago)
end
Which does seem to return something, if I do an #updates.total it returns the number of records I was expecting to find. Beyond this I'm not sure how to actually make use of the records. What I'd like to do is send #updates to a view and determine the model type of each record and then proceed to print out the relevant information, i.e names, descriptions, parent/child record information (for instance upload.user.username).
I might be going at this all wrong, perhaps there's a better option than sunspot for the simple search I'm attempting to perform?
Refer readme for details of how to use the search results. The method you are looking for is "results", which will give you first 30 results, by default:
#updates.results # array of first 30 results
I'm trying to find the best way to query both news feed and wall using a single request.
First attempt:
Query me/home and me/feed in batch request.
Problem: querying me/home gives me bad results due to Graph API bugs (showing blocked items and on the contrary not showing some items that should be shown) so I decided to change to FQL which seems to handle it much better.
Second attempt:
Use single batch request to query:
(1) me/feed directly.
(2) fql.query for stream table with filter_key set to 'others'.
Problem: Needs to also query for user names because the stream table contains only ids.
Third attempt:
Use batch request to query:
(1) me/feed directly
(2) fql.multiquery for stream table with filter_key set to 'others' and the names table with "WHERE id IN (SELECT actor_id FROM #stream)".
Problem: Fails. It returns "Error: batch parameter must be a JSON array" although it is a json array.
Fourth Attempt:
Use fql.multiquery to get news feed stream, wall stream and names.
Problem: I have no idea how to get a view similar to me/feed using FQL. The best I could get is a list of all my own posts but it doesn't show photos the user is tagged in (so I guess more things are missing).
Appreciate any hints.
Due to FQL not doing SQL style joins, getting information from multiple tables in one query is currently impossible.
Use FQL on the stream table to get the list of posts you want to display be sure to grab the source_id. The source_id can be a user id, page id, event id, group id, and there may be more objects too, just don't remember off the top of my head. (You may also want to do similar caching of the actor_id, target_id and viewer_id)
Cache the source_ids in a dictionary style data cache with source_id being the PK.
Loop thru the cache for ones you don't have information on
Try grabbing the information from the user table based upon id, then next the page table, then event table, and group table until you can find what that ID belongs to. Store the information in your cache
For display merge together the stream table items with the source_id information.